Fairly regularly the video or graphics in a given application will freeze. The audio will continue, but in order to have the video or graphics refresh I have to either move the window around (i.e. grab the title bar and move the window slightly), or select another app and then go back to the offending app either by clicking on another app and then back to the first or by command-tab to another app and then quickly command-tab back to the first. It's not app-specific, however; when it's happening, it'll likely happen to any app with dynamic content. I see it most often when playing back video (either local or streamed, and regardless of whether using Quicktime Player, VLC, or Quick View from the finder). For non-video apps it shows up as screens which don't refresh, e.g. I'll click on a radio button and I can hear via the hard drive that some activity is taking place but won't see anything update until moving the window.

It's possibly triggered by having a fair number of apps open (i.e. triggering swapping), but I haven't been able to verify this. It also comes and goes, and the Mac going to standby and then being woken up may help; rebooting almost always fixes it for a period of days or longer, but eventually it comes back.

I have an underlying suspicion that it might be related either to Parallels or to a graphics driver, but the symptoms persist regardless of whether a Parallels session is active.

Any ideas on what the problem might be or where to track down further clues? I've been able to find nothing similar in searching here and elsewhere online, which suggests it might be a Mac Pro and/or Parallels-related issue (I don't see this behavior on my Macbook Pro).

MacRumors attracts a broad audience
of both consumers and professionals interested in
the latest technologies and products. We also boast an active community focused on
purchasing decisions and technical aspects of the iPhone, iPod, iPad, and Mac platforms.